Equipment for inserting small flexible tubing into high-pressure wells



p 195i 7 G. H. CALHOUN ET AL 7, 9

EQUIPMENT FOR INSERTING SMALL FLEXIBLE TUBING INTO HIGH-PRESSURE WELLS Filed June 24, 1948 5 Sheets-Sheet l \nvzni'ors: George H. Calhoun Herbzri' Allen Sept. 4, 1951 G. H. CALHOUN ET AL 2,567,009

EQUIPMENT FOR INSERTING SMALL FLEXIBLE TUBING INTO HIGH-PRESSURE WELLS Filed June 24, 1948 5 Sheets-Sheet 2 o 0 E o 1 O 3 J '55 122 :23 2% c j; j

Fl'q I \nvrzrfl'ors: George H. Calhoun Herbcr+- Allen Sept. 1 51 G. H. CALHOUN ET AL 2,567,009

4 EQUIPMENT FOR INSERTING SMALL FLEXIBLE TUBING INTO HIGH-PRESSURE WELLS Filed June 24, 1948 5 Sheets-Sheet 5 \nvcnfors: Gzorqz H. Calhoun Hzrberf Allen P 4, 1951 G. H. CALHOUN ETAL 2,567,009

EQUIPMENT FOR INSERTING SMALL FLEXIBLE TUBING INTO HIGH-PRESSURE WELLS Filed June 24, 1948 5 Sheets-Sheet 4 Fig. G

p 4, 1951 v G. H. CALHOUN ET AL 2,567,009

EQUIPMENT FOR INSERTING SMALL FLEXIBLE TUBING INTO HIGH-PRESSURE WELLS Filed June 24, 1948 5 Sheets-Sheet 5 Fig. 8

\nvmmrs: G-(cor'qz H. Calhoun Harbin"? Allen Patented Sept. 4, 1951 EQUIPMENT FOR INSERTING SMALL FLEX- IBLE TUBING INTO HIGH-PRESSURE WELLS George H. Calhoun and Herbert Allen, Houston, Tex., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application June 24, 1948, Serial No. 35,004

Claims.

This invention relates to oil well tools and pertains more particularly to apparatus for inserting strings of elongatedcylindrical or tubularelements, such as tubing, cables, etc., into a highpressure well, suspending said strings therein, and subsequently removing them from the well.

Since the present invention is especially well suited for handling strings of small diameter flexible tubing, it will be described herein in its application to this particlular type of operations. It is, however, understood that the invention is in no way limited thereto, and that by suitably enlarging or modifying the various component parts of the present system, said system can be readily adapted, without departing from its principle, for the handling of any type of production tubing, as in snubbingoperations, etc. The invention may also be used for inserting temperature and pressure bulbs, or similar instruments, into pressure vessels such, for example, as towersin oil refineries.

1 It is often desirable, during the operation of a well flowing under pressure, to introduce fluids,

for example, liquid corrosion inhibitors, into the well flow stream far down the production tubing in the well. In order to discharge liquid inhibitors into the well flow stream at any desired location, it is necessary to conduct said inhibitor to the desired point through a conduit or tubing having a sufficient capacity to handle the flow of liquid inhibitor therethrough. Generally, only small quantities, for example, two gallons per hour, of an inhibitor are injected into the flow stream of the well so that the conduit carrying the fluid inhibitor may be sumciently small to be insertable in a production tubing string. Thus, a suitable conduit from the standpoint of economy, capacity, ease of transporting and handling and length of life, is a flexible, corrosionresistant tubing of small diameter.

Since small diameter flexible tubing has relatively thin walls, it is extremely difiicult to insert it through a pressure packing without bending the tubing, which weakens its walls and I makes it unsuitable for further use.

inserting devices are not'capable of maintaining the easily-bendable tubing in rigid alignment at substantially all points between the gripping ele-' ments and the seal or lubricator element through which the tubing is being'forced, thus increasing the chances of bending said tubing.

It is therefore a primary object of this invention to provide apparatus for rapidly inserting small-diameter flexible tubing or equivalent elongated cylindrical elements into a high-pressure well and removing said tubing therefrom.

It is also an object of the present invention to provide a suspension and pack-off mechanism equipped with detachable clamping means for suspending a small-diameter flexible tubing in a well after the inserting mechanism has been removed.

A further object of this invention is to provide an inserting mechanism having gripping elements adapted to grip a smooth-surfaced, smalldiameter, flexible tubing over a substantial portion of length thereof without injuring said tubing during insertion into or removal from a well,

Another object of the present invention is to provide a tubinginserting mechanism adapted to maintain the tubing in rigid alignment while inserting it into a well, thus preventing any bend-Y ing or buckling of said tubing. 1

Still another object of this invention is to provide a tubing inserting apparatus having prime mover means for rapidly inserting a small-diameter flexible tubing into a high-pressure well, said.

prime mover means receiving its power from an outside source or from the pressure of the Well where the tubing inserting apparatus is beingused.

Other objects and advantages of the invention will become apparent from the following description taken with reference to the drawings wherein: I

Figure 1 ,is a diagrammatic elevation view, partly in cross section, o f an embodiment of the present tubing inserting mechanism.

Figure 2 is a top plan view of Figure 1.

Figure 3 is a cross-sectional view of the present device taken along the line 33 in Figure 2.

Figure 4 is a view in cross section taken along the line 4-4 in Figure 1.

Figure 5 is an isometric view of an interme-- diate link of the chain employed in the-tubing. inserting mechanism.

Figure 11 is a cross-sectional view of the tubing clamping means employed in the present invention.

Briefly, the apparatus of the present invention comprises casing closure means adapted to be mounted on and close a high pressure well casing, there being a vertical bore in said closure means through which a small-diameter flexible tubing may ,be introduced into said well casing, packing means in said casing .closure means forming a fluidtight seal about a tubing passing through said axial bore, movable tubing gripping means detachably mounted directly above said vertical bore in the casing closure means for conveying said tubing through said bore, tubing alignment means mounted between said gripping means and said axial bore, and adjustable clamping means carried by said casing closure means for suspending tubing within the well casing.

.Referring to Figures 1 and 3 of the drawing, the casing closure means, as shown, comprises a cylindrical body It] having an axial bore ll therethrough, which bore is enlarged at its lower endand threaded at 12 to receive and secure therein a stripper l3. The stripper [3 has an axial bore 14 therethrough that is coaxial with the bore ll. Secured to the lower end of said body [0, in any desired manner as by screwtlireads'or welding, is a suitable means, such as a coupling 5.!5, for se'curingsaid casing closure means to. a threaded section on the top of a well casing.

The upper part of the axial bore 1 I is enlarged and threaded at IE to accommodate athreaded gland member ll therein. An axial bore H3 in said gland member I! is coaxial with the bore ll. A'radially, extending passageway IS! in the cylindrical body 10, between the outside thereof and the axial bore I I, is threaded at 26 to secure therein a packing injection assembly 2 I, through which any suitable packing material may be introduced. If desired, the lower end of the gland member 11 may, as in this embodiment, be recessedat its lower end to accommodate sealing rings 22 and a gland spacer 23 therebetween. The lower end'of said gland member I! has a plurality of radial openings 24 therein so that one of themis substantial-1y iniregister with passageway 19 in the body 10 whereby packing material may be introduced into said body l0 and gland member I! and distributed about the axial bore [8 therein-to form :a fluidtig'ht seal about the tubing to be positioned in said bore.

A coaxial recess 25 is drilled and tapped in the top of the gland member H. A threaded nut 25 having a tapered axial bore 21 therethrough-is secured in the gland recess 25. Mounted above saidgland member I! and nut 26 is a plate mem ber 28 that is secured to said body It by any suitable means as by stud bolts 29 and nuts 30. A hole '3lthrough this plate 'member 28 is threaded to receive the threaded portion'of an auxiliary alignment and clamping means, such as a collet 32.

As shown in Figure 11, the collet 32 comprises a cylindrical body member 33 having a threaded portion 34fand antaxial bore' 35 therethrough of a dimension slightly greater than the diameter of a tubing, cable, or wire to be run therethrough, as will be later described. The lower end 36 of the collet32 is tapered at 31, to substantially the same angle as the tapered bore 21 of the nut 26 (Figure 3). Adjacent the tapered portion 31, the collet 32 is machined, as at 38, to reduce the thickness of the collet wall and to make it more flexible. Thus, when a longitudinal slot 39 is cut or formed in the tapered and machined lower end 36 of the col1et,' a tubing clamping means is formed. The upper end 40 of the collet 32 is also tapered and if desired may have flats 4| formed at the point of the taper to serve as additional tubing alignment means.

The collet is threadedly secured in the center of the plate member 28 with its tapered'lower end 36 in the tapered axial bore 21 of the nut 26 (Figure 3')-'.' The position ofth'e' collet-32 -is-f-lxedby any suitable means as by a lock nut 42.

A small pipe coupling 43 is positioned about the collet 32 above the plate member 28, said coupling being fixedly secured to said plate member 28 or said nut 42 in any suitable manner as by welding." Flange means 44-are securedyasmywelding; to the cylindrical body 1 0 of the casing" closure means. A conduit 45 may also be formed in said body in communication between the axial bore therethrough and the space outside thereof, said conduit 45 being normally closed by a 52, having a centrally located hole 53 there--' through (Figure 2), joins the frame members 41, 48, 49 and 50, being-fastened thereto by bolts 54.

Holes 55 (Figure 1) are drilled through the lower portion of each of the frame members 41, 48, 49 and 50, each of said holes being in alignment with the hole in the opposite frame mem ber and being fitted With'a bearing 56. Rotatably mounted in bearings 56 are parallel shafts 51 and 58 as shown in Figure 4. Fixedly positioned on said shafts 51 and 58, between the bearings 56;" are -'-twopairs" -of -'ide'rrticalspacedsprocket wheels -59 "-and 60, 6 and; respec-- tively. Secured to the corresponding ends of said shafts 5! and Stare-meshing drivegears 63 and 64. Collars 65' and 66 are affixed at the other ends of said shafts 51 and 58 adjacent the bearings 56.

A second set of shafts 51 and 63, having spaced sprocket wheels 69, 70, H and 12 afiixed thereto, are rotatably mounted in bearings'l3, I4, 15 and 16 in the upper portion of the framework as shown in Figures 1 and 3. However, these bearings 13,14, and 16 are 'slidably movable in vertical slots TI, 78, 19 and in the frame members 41, 48, 49 and 50, beingv positioned therein at any desired point byadjusting screws BI, 82, B3 and 84 having lock nuts 85, 86, 81 and 38. v v

Mounted between lower sprocket wheels 59 and 60 and upper sprocket wheels 69 and I is an endless chain 89 which is preferably three links wide. The outer links 90 and 9| of said chain are conventional roller links while the intermediateilinks 92 are of special design embodying a gripping surface on its outer face. Each roller link 90v and 9| has an arcuate inner edge 93 .to substantially conform with the edges of the sprocket wheels 59, 60, 69 and I0, this relation being clearly shown in Figure 3.

Eachintermediate link 92 (Figure ispreferably block-shaped, having curved ends 94 and 95, fiat sides 96, top face 91 and bottom face 98. Formedor cut in the top face 91 of said link is a longitudinal semi-circular groove 99, preferably havin a radius equal to the outside radius of the tubing or other element to be put through this apparatus. Two horizontal holes|00 and |0| drilled through said link serve to accommodate connecting pins. The intermediate links 92 are identical in shape and size and preferably have a greater height than the roller. links so that the top or contact faces 9! of said intermediate links 92 extend forward of the roller links 90 and 9| when the endless chain is in a vertical .position as shown in Figure 3. These links 92. are preferably made of steel but may be made of any other metal, composition material, rubber, or the like. In assembling the endless chain 09 the outer roller links 90 and 9| and the intermediate links 92 are fastened with their flat sides together by means of link pins I02 (Figure 3) which extend through the three links 90, 9| and 92.

A second triple-width endless chain I03, identical to the above-described chain 89, is mounted between the other pair of upper and lower sprocket wheels II and I2, 6| and 62, respectively. With the two chains 89 and I03 mounted face to face, the grooves 99 in the faces of the intermediate links 92 of each chain are in the same vertical plane. When the oppositely faced links 99 are brought in face to face contact, the semi-circular grooves 99 form a substantially cylindrical opening having a diameter equal to, but preferably slightly less than, the outside diameter of. the tubing to be inserted into the well casing.

Spacin means, for governing the position of the two chains 89 and I03 and hence the position of the opposing intermediate blocks 92 with regard to each other, are supplied by two pairs of vertical bar members or press-up blocks I04 and I05, I06 and I0! as shown in Figures 3 and 4.

One pair of vertical bar members I04 and I05 are aifixed, in any suitable manner, as by Welding, to a pair of horizontal bar members I08 and I09 (Figures 1 and 3) which in turn are mounted, for sliding movement in a, horizontal plane, in openings IIO, III, H2 and H3 in the vertical frame members 41 and 48. Bar positioning means, such as positionin screws II4 having lock nuts II5, are fixedly secured to the vertical frame members 41 and 48 so as to contact the horizontal bar members I08 and I09.

The vertical bar members I04 and I05 have a length less than the distance between the upper and lower pairs of sprocket wheels 69 and I0, 59 and 60 and preferably a width slightly less than the width of the rollers in the links 90 or 9|. The vertical bar members I04 and I05 are positioned inside the endless chain 89 so that each bar memher is in contact with the rear face of said chain I 89 on the side that is adjacent the other chain I03. Preferably, the distance between the vertical bar members I04 and I05 is equal to the distance between the roller links and 9| so that only the links 90 and 9| of the chain 89 are in contact with said bar members.

The second pair of vertical bar members I05 and I01 (Fig. 3) are identically arranged on a pair of horizontal bar members III; and I I! movably mounted in slots H8, H9, I20, and |2| in the vertical frame members 49 and 50, said horizontal bar members H6 and II! being positioned in said slots by positioning screws II'4. Thus, by adjustment of the positioning screws II4, an accurate alignment of the intermediate links 92 over the collet 32 may be secured. Also, when a tubing is being conveyed between said chains 89 and I03 into a well, the gripping pressure exerted on said tubing by the grooved intermediate links 92 of both chains may be regulated, as desired, by adjustment of said positioning screws II4.

Since the drive gears 63 and 64' attached to the shafts 5'! and 58 are in mesh, movement of either shaft causes both chain belts 89 and I 03 to rotate simultaneously in opposite directions so that oppositely facing links move upward or downward at the same time. The belts 89 and I03 may be rotated manually by handle means I22 and I23 (Figure 1) secured to the ends of shaft 51. If desired, any suitable mechanical, electrical or hydraulic prime mover means may be secured to one of the shafts 5'! or 58 to drive the attached chain belts 89 and I03 as diagrammatically shown in Figure 6. Both the prime mover means I44 and the tubing-inserting apparatus may be mounted on a common platform I24 adapted to be secured to the flange means 44 of the casing closure means. The prime mover means may be an air or gas operated reversible engine which may be powered from any desired source such, for example, as the well itself. A suitable'safety shield I25 (Figure 1) may cover the drive gears 03 and 64, being secured to the vertical frame members 41 and 50. The two chain belts 89 and I03, and the element being gripped thereby, may be temporarily maintained at any position by inserting a holding pin I26 through suitable holes or openings in said shield I25, drive gear 63 and vertical frame member 41.

For illustrative purposes, an application of the present invention will be described with regard to the insertion or withdrawal of small-diameter flexible tubing into high pressure wells, which may be done for various purposes, such as the measurement of well potentials or the injection of corrosion-inhibiting compounds. When the main purpose of inserting a small-diameter flexible tubing I21 (Figure 6) into a high pressure well is to allow a corrosion inhibitor to be discharged into said casing at some predetermined depth, say 5000 feet, the size and type of tubing used must necessarily be determined by the amount of inhibitor (gallons per hour) to be introduced into the well and the conditions encountered therein. A relatively flexible tubing is preferred .in order to facilitate its storage and transportation in a reasonably convenient manner, as on a reel I28 mounted on a small trailer I29 (Figure 6). The tubing may be made of any suitable metal or plastic material having the desired relatively high structural strength and corrosion resistance. Short sections of metal tubing may be joined together to form a single length of tubing in any suitable manner, as by silver soldering, welding, or the like. Sections of plastictubing may be bonded together with suitable tubing be joined together so as to give a. flush joint that is'readily accommodatedin the grooved' link faces of the inserting chains 89 and I03. However, small couplings may be used to connect seotionsof tubing if the intermediate links 92 of the-chains 83 and I93 are made of, or faced with, a resilient material, such as synthetic rubber. Couplings, if used, may also be arranged to move and fit in the spaces I39 between the adjacent links 92 of the chains.

To facilitate the insertion of tubing into a well casing and to prevent plugging of the tub ing during said operation, a valve-equipped sinker bar I3I may be attached to the lower end of the tubing. As shown in Figure 7, the sinker bar I3I comprises a weighted lower end I32, a valve body I33 having an axial bore I34 therethrough which is enlarged and tapped at one end to receive a nipple I35 and is enlarged at the other end to form a valve chamber I36 accommodating a ball-type check valve I31 and its actuating spring I38. A nipple I39 that is secured to the lower end of the tubing I21 in any suitable manner, as by welding, serves as means for connecting said tubing to said sinker bar. Fluid outlet means I40 through the walls of said valve body I33 are'normally closed-by said spring-loaded non-return valve I31.

Before running a small diameter flexible tubing into a well against pressure, the assembled tubing inserting mechanism and its related equipment is moved into position adjacent a well head and the former is mounted at the top of the well casing I4I above the master control valve I42 as shown in Figure 6. A guide sheave I43 is temporarily secured in any suitable manner, as by bolting, to the top of the apparatus. sheave I43 acts as a guide between the tubing reel-l28'and the inserting chains 89 and I 03.

,The end of the tubing I21 is unwound from the reel I28 and passed over the sheave I43 (Figure 6) and through the hole 53 (Figures 2 and 3) in, the center of the top plate 52. The tubing is then run between the chains 89 and I03 in the grooves 99 of the intermediate blocks of said chains and then through the coaxial bores of the collet 32, gland member I1, cylinderbody I and stripper I3 so that the end of the tubing I21 projects out of the stripper I3. The nipple I39 (Figure-'1) is then fixedly secured to the end of the tubing and the sinker bar I3I is attached to said nipple and allowed to hang just below the stripper I3.

- The completely assembled apparatus is now mounted by means of its threaded coupling I5 to the topoi'a short extension pipe I45 (Figure 6) that is in turn fixedly secured in fluidtight manher to the top of the master valve I42 of the well. The extension pipe I45 is of sufficient length to receive the sinker bar I3I and is threaded at one end to mate with coupling I5 while the other end is adapted to be removably secured to the master control valve I42 in any suitablemanher as, for example, by bolts I46. The tubing I21 in the axial bore II (Figure 3) of the body IIl of the casing closure means is packed 01f in a fluidtight manner by introducing a suitable pack ing through the packing injection screw 2|. Any other suitable sealing or packing-off means may be used, said means being located in or mounted on the body member I0. For example, a rubber pack-off element may be mounted on the top of the body I0 abouttubing I21.

With the top of thewell casing I-4I now sealed off in a flnidtight manner, the master control valve I42 is opened to allow the sinker bar I 3I and attached tubing to pass through into the wellcasing below. The motor I44 is then started in theproper direction to drive the chains 89 and I03, causing the grooved intermediate links 92 to'grip the outer surface of the tubing and force it into the well. It will be noted from Figure 3 that a substantial portion of each chain 89 and I03 contacts and grips a substantial area of the tubing that is run between them, thus maintaining suflicient pressure. and therefore friction, against tubing to force it through the seal of said casing closure means. While gripping and inserting the tubing, the chains also maintain it in perfect alignment over said collet 32, thus preventing any bending or buckling of said tubing.

A particularly important feature of the present invention is the fact that the tubing inserting mechanism is detachable from the casing. closure means. At the end of a downward run of tubing. into a well, the tubing is clamped securely in position. by tightening nut 26 (Figure 3) against the split, tapered, lower end 36 of the collet 32 causing it to clamp the tubing I21 andthus preventing further downward or upward movement of said tubing. The tubing is then cut off at some point above the inserting mechanism and the sheave I43 and tubing inserting mechanism may be removed for use on another well. Cutting off the tubing above the apparatus leaves a suflicient length for the inserting mechanism to grip when said mechanism is later again installed to remove said tubing from the well. A short section of pipe I 41 (Figure 8) may be inserted over the projecting tubing I21 to protect it, said pipe being. threadedly connected to coupling 43 surrounding. the collet 32. A suitable coupling I48 may be afiixed to the end of the tubing I21 whereby a pump tubing I43, leading from the outlet of a chemical injection .pump I50 may be coupled thereto. Chemical corrosion inhibitor fluid may then be pumped down the well casing through said tubing I21 and be discharged under pressure; through the check valve in the sinker bar I3I.

To reverse the operation and pull the flexible tubing I21 and sinker bar I3I from the well, the pump tubing I49 is disconnected and the short section of pipe I41 is removed. The assembled tubing inserting mechanism, prime mover I44 and sheave I43 are mounted on the flange 44 below the collet 32. The tubing I21 is' inserted between chains 89 and I03 and the direction of the prime mover I44 is reversed. Starting the prime mover I44 in the reverse direction causes the portion'of the chains 39 and I03 facing each other to rotate upward pulling the flexible tubing I21 out of the well. When all of the tubing I21 is out of the well the sinker bar I3I is positioned in the short pipe section I45. The wellhead master con trol valve I42 is then closed and the tubing inse'rting mechanism and the casing closure means may be removed as a single unit either by dis-' connecting the coupling I5 or by unbolting the short pipe section I45 from the valve I42. The apparatus may then be readily moved to another. wellhead.

It is understood that although the preferred embodiment of the present invention has been described above as having a tubing inserting mech'-' anism comprising a pair of triple width endless chains having grooved intermediate links, it} is, clear that single width chains could be employed instead if the faces of the chains that are in substantial contact with each other possess longitu 'dinal grooved portions capable of gripping a'tubing. A section of one embodiment of such a chain I54 having downwardly extending arms I55 secured to the pins I53. Each plate member I54 has a longitudinal groove I56 in its face adapted to fit against a tubing. While the use of roller link chains is preferred, any other type of belt means may be used, such as for example, any ordinary drive belt made of rubber, cord, wire and the like having sufficient thickness to have a groove cut or formed in its outer surface. Such a belt would be run between a pair of sheaves instead of sprocket wheels.

It is also understood that although this invention has been described for illustration purposes chiefly with regard to the insertion into wells of small diameter flexible tubing, it can equally well be applied for the insertion of any other elements of substantial length, particularly when said elements are of such nature as to be easily damaged during insertion, as for example in the case of insulated conductor cables.

As used in the foregoing description and in the claims appended thereto, the term string element refers to any tubing, electrical conductor cable, wire line, or the like which may be employed in a high-pressure well installation.

We claim as our invention:

1. An apparatus adapted to be mounted on a well head for inserting an elongated semi-rigid string element into a high pressure well casing, said apparatus comprising casing closure means mounted on the well head and having a vertical bore therethrough through which said string element may be inserted, said bore having a diameter slightly greater than the outside diameter of said string element, means carried by said closure means adapted to seal the vertical bore of said casing closure means in a fiuidtight manner about the string element positioned therein, a gripping and feeding mechanism positioned directly adjacent said casing closure means for gripping and feeding said string element through said vertical bore and sealing means, and adjustable clamping means carried by said casing closure through which said string element passes for anchoring the string element in the well casing.

2. In an apparatus for inserting an elongated semi-rigid string element into a pressure wellhead and casing, a closure member for said wellhead having a vertical bore therethrough through i which said string element may be inserted, packing means carried by said closure member adapted to seal said vertical bore against loss of well pressure when said string element is inserted therein, clamping means carried by said closure member for anchoring the string element therein, a gripping and feeding mechanism positioned above the wellhead, said gripping and feeding mechanism comprising at least two pairs of wheel elements mounted symmetrically with regard to said vertical bore, one wheel element in each of said pairs being mounted above the other in the same vertical plane, two endless belts each mounted on eachof said pairs of wheel elements, said two belts having gripping elements thereon with vertically extending gripping surfaces substantially adjoining each other along the center line of said vertical bore, and means for rotating said wheel elements so as to cause said adjoining grip- I ping elements to move together in the same direction, whereby a string element inserted into said vertical bore is frictionally engaged by said gripping elements and driven along a vertical line through said vertical bore and the packing means therein.

3. In an apparatus for inserting acylindrical semi-rigid string element into a pressure wellhead and casing, a closure member for said wellhead having an axial bore therethrough through which said string element may be inserted, packing means within said closure member adapted to seal the space between the walls of said axial bore and .said string element when said string element is inserted therein, clamping means carried by said closure member for anchoring the string element therein, a gripping and feeding mechanism removably positioned above the wellhead, said gripping and feeding mechanism comprising at least two parts of wheel elements mounted symmetrically with regard to said axial bore, one wheel element in each of said pairs being mounted vertically above the other and separated therefrom by a distance greater than the diameter of said wheel elements, two endless belts each mounted on each of said pairs of wheel elements, said two belts having gripping elements thereon with vertically extending gripping surfaces substantially adjoining each other along the center line of said axial bore, and means for rotating said wheel elements so as to cause said adjoining gripping elements to move together in the same direction whereby a string element inserted into said axial bore is frictionally engaged by said gripping elements and driven along a vertical line through said axial bore and the packing means therein.

4. In an apparatus for inserting a cylindrical semi-rigid string element into, a pressure wellhead and casing, a closure member for said wellhead having an axial bore therethrough through which said string element may be inserted, packing means within said closure member adapted to seal the space between the walls of said axial bore and said string element when said string element is inserted therein, clamping means carried by said closure member for anchoring the string element therein, a gripping and feeding mechanism removably positioned above the wellhead, said gripping mechanism comprising two endless belts having gripping elements thereon with vertically extending gripping surfaces substantially adjoining each other along the center line of said axial bore, and means for driving said belts with said adjoining gripping elements traveling in the same direction, whereby a string element inserted into said axial bore is frictionally engaged by said gripping elements and driven along a vertical line through said axial bore and the packing means therein.

5. The apparatus of claim 1, having an elongated tubular guide aiiixed to said closure member and extending thereabove at least to the level of the lower wheel elements, said guide having an axial bore in register with the bore of the closure member, whereby each successive increment of a string element being moved downward by said gripping belt elements enters said guide bore substantially as it is released by saidgripping elements and is thus protected from buckling.

6. The apparatus of claim 1, wherein said adjustable clamping means comprises a guide element with a resilient wall portion and gland means in screw-threaded engagement between said closure member and said resilient wall portion, whereby a circumferential pressure can be applied to said' guide portion by an adjustment of said gland means to cause said guide element to grip said string element to suspend it in the -'Well after the completion of the lowering operation.

7'. The apparatus of claim 3 including means carriedby said gripping mechanism for adjusting the spacing of the substantially adjoining gripping elements of said belts to accommodate said cylindrical string element between themand to maintain pressure in a transverse direction less belts consist of roller chains, each of said chains being mounted between a pair of sprocket wheels and comprising a plurality of links, con- .necting pins securing said links together, and

grooved plate elements secured on the outer face of said links, said plate elements being adapted to grip said string element.

10'. The apparatus of claim 3- wherein each of 12 said endless: belts consistsof; a itriple-widthnendless chain. comprising three single width chains with connecting pins fastening said three single chains in side-by sid'e:relationship, the outer chains. consisting ofroll'erlinks and; the intermediate chain consisting of: plate links having longitudinal. grooves in. the top surfaces, andwherein said wheel-elements; consist of apair of spaced sprocketwheel's on which said outer roller chains areitmounted.

GEORGE H. CALHOUN. HERBERT ALLEN.

REFERENCES: CITED The following references are of record' inthe file of this patent:

UNITED STATES PATENTS Number Name Date 1,579,260 Tiller Apr. 6, 192.6 1,586,923 Townsend.--- i June 1,. 1926 1,817,201 Minor Aug.. 4, 1931 1,865,007 Hickset al June 28, 1932 13,904,885 Seeley Apr. '18, 1933 2,046,997 Boddy etal July 7, 1936 2,097,016 Bowen Oct; 26, 1937 

